Capacity calculation

[ano]

I must've seen this asked before, but the power of the search fails me. So say I've got a 5 gallon FV as my mash tun, lets say it's 25 litres as there's space at the top, how much grain/liquor can I fit in it if fly sparging and how much less if batch sparging? Or what else do I need to know to work it out?

Basically if I wanted to make a 7% stout for christmas how much could I make?

 

[prolix]

for a 23L length you will be looking at about 8 kg of grain as efficiencies are lower generally at higher gravities.

at a grain liquor ratio of 1:2.5 you will be almost full at 20l plus grain and definitely fly sparging. I would drop the ratio down to 2 that should give you about 20 litres of mash.

Personally I would do three batches first just drain the mash then fill up sparge and drain see how much wort you have/ need to get boil volume, then add that and sparge again. efficency might take a beating but increase the boil time to reduce the length and get that gravity.